ACCOMMODATION presentation its mechanism

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1. ACCOMMODATION DR. SAYANTANI MANDAL 1 ST YEAR PGT RIO KOLKATA

2. DEFINITION THE MECHANISM BY WHICH THE EYE CHANGES ITS REFRACTIVE POWER BY ALTERING THE SHAPE OF LENS IN ORDER TO FOCUS OBJECTS FOR NEAR.

3. THEORIES : HELMHOLTZ THEORY : CONTRACTION OF CILIARY MUSCLE CHOROID IS PULLED FORWARD RING OF CONTRACTION DEVELOPS AND THERE IS RELEASE IN TENSION OF THE ZONULES UNIFORM REDUCTION IN TENSION ON ALL ZONULAR FIBERS

4. LENS UNDERGOES THE FOLLOWING CHANGES INCREASES IN THE CURVATURE INCREASE IN ANTERO-POSTERIOR DIAMETER DECREASE IN EQUATORIAL DIAMETER FORWARD MOVEMENT OF ANTERIOR POLE

5. PHYSICAL ACCOMMODATION : - ACTUAL DEFORMATION IN THE SHAPE OF THE LENS MEASURED IN DIOPTRES PHYSIOLOGICAL ACCOMMODATION : - CONTRACTION POWER OF CILIARY MUSCLE EXPRESSED IN MYODIOPTRES FAR POINT : MAXIMUM DISTANCE AT WHICH AN OBJECT IS SEEN CLEARLY WHEN ACCOMMODATION IS RELAXED AND REFRACTIVITY OF EYE IS MINIMUM NEAR POINT : NEAREST DISTANCE AT WHICH THE EYE CAN SEE CLEARLY WITH MAXIMUM EFFORT OF ACCOMMODATION AND REFRACTIVITY OF THE EYE IS MAXIMUM

6. RANGE OF ACCOMMODATION : - DISTANCE BETWEEN THE FAR POINT AND NEAR POINT AMPLITUDE OF ACCOMMODATION : - TOTAL ACCOMMODATION EXERTED BETWEEN FAR POINT AND NEAR POINT

7. ANOMALIES ANOMALIES OF ACCOMMODATION 1) HYPERACCOMMODATION 2) HYPOACCOMMODATION

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